'The beginning of the end' of NATO?

Russian President Vladimir Putin has taken the Obama administration's idea of a "reset" in relations and turned it into a wedge, which experts say he's using to try to break the NATO alliance.

It's no secret: Since Russia annexed Ukraine's Crimea in March 2014, the Kremlin has ramped up the pressure on NATO as well, especially in the Baltic states of Estonia, Latvia and Lithuania, which used to be part of the Soviet Union. And alliance leaders have scrambled to find ways to react to the Kremlin's more aggressive posture and reassure members of its relevance to their security.

But in recent weeks, a number of current and former officials, along with several Russia experts, have warned that Putin's gambit to split the transatlantic compact and redefine international security relationships to Russia's advantage appear to be working.

"Before us is emerging one of the premiere strategic challenges of the post-Cold War period," said retired Marine Gen. James Jones, a former NATO supreme allied commander in Europe who also served as White House national security adviser from 2009-2010.